The invention relates to an absorbent single-use article an absorbent element for storing bodily fluids and a back sheet which is fluid impermeable at least in sections, where the fluid-impermeable is provided with a moisture indicator
The need has long existed for indicating saturation of an absorbent single-use article by suitable means. Different moisture indicators for this have become known. The moisture indicators are provided predominantly in the area of the absorbent element and on the side of the absorbent element facing away from the body to indicate saturation of the absorbent element.
Moisture indicators are known based on pH indicators which, depending on the pH value, show a change in color when saturated with bodily fluids and indicate saturation. Such discoloration is frequently hard to distinguish with respect to the low contrast, for example, from yellow to pale blue. These pH indicators can, for example, be applied as part of a hotmelt compound (U.S. Pat. No. 5,035,691). The production of hotmelt moisture indicators and their application, mostly by means of slot nozzle application, is complicated.
In addition, moisture indicators based on water-soluble inks are known and described, for example, in EP 0 211 524 B1. Such moisture indicators are supposed to dissolve and disperse on contact with bodily fluids. They can be applied, for example, by printing units, specifically by ink-jet printing, to suitable components of the single-use article, specifically to its backing sheet. Thus EP 0 211 524 B1 describes the imprinting of an impermeable plastic film as the backing sheet with water-soluble dye, for example in the form of graphics which change under the effects of bodily fluid, specifically become blurred.
When moisture indicators of the last named variety are used with single-use articles having microporous breathable films as the back sheet, problems concerning visibility result. The microporous films are in general relatively opaque since, as a result of the air-filled pores, different changes in the index of refraction lead to high opacity (milkiness). In this respect it has already been proposed to post-treat the films in a suitable way thermally and/or mechanically and thereby achieve a reduction in the opacity, i.e., improved transparency (EP 0 553 808 B1).
On the other hand, there is a fundamental problem with the functioning of the moisture indicator when using such moisture indicators based on water-soluble systems, such as water-soluble inks, in conjunction with microporous breathable film materials. No satisfactory moisture indicators are known in conjunction with microporous breathable films. It has been proposed to apply the moisture indicator on or in the proximity of a strip, separate from the backsheet, said strip differing in color from the remaining backsheet material so that the location where the moisture indicator is applied is more easily identifiable to careworkers. However, the fundamental problem of the unsatisfactorily functioning moisture indicator on a water-soluble ink base was not solved.
Even in accordance with EP 0 813 850 A2, this fundamental problem of the inadequate functioning of such moisture indicators with microporous backsheets is not solved; instead the moisture indicator is applied to an additional layer separate from the backsheet, which raises production costs, reduces contrast and compromises recognizability.
It would, therefore, be desirable to provide a satisfactorily operating, simple and economical moisture indicator system for absorbent single-use articles with a breathable backsheet.